In the transmitter system, the baseband signal is processed with digital-analog conversion, low pass filtering, local oscillating (LO) signal mixing, in-phase and quadrature signal combination, band pass filtering and the intermediate frequency (IF) signal mixing, so as to generate a radio frequency (RF) signal. These processions can be implemented by a plurality of circuits, and the in-phase and quadrature baseband signals processed by the circuits of in-phase and quadrature channels (I and Q channels) may have offset due to the semiconductor process variations. The offset is named I/Q imbalance, and a calibration or correction should be done to deal with the I/Q imbalance (comprising I/Q gain and phase imbalances).
The analog-digital converter (ADC) can be used to sample the processed RF signal for calibration of I/Q imbalance, and the sampling rate of the ADC should be larger than the signal bandwidth of the RF signal. However, for the transmitter system adopting the communication band of the millimeter wave, the signal bandwidth is ultra large, for example several giga hertz (GHz), and thus the ADC should have the sampling rate of several giga bits per second (Gb/s). It is a challenge for designing an ultra-high sampling rate ADC, and even the ultra-high sampling rate ADC can be designed well, the large power consumption due to the ultra-high sampling rate effects the heat dissipation of the transmitter system.